Process for drying boards and the like.



J. VOGT.

PROCESS FOR DRYING BOARDS AND THE LIKE.

APPLICATION Hill) 0CT.25,19A13. Lln meme@ Apr., 6, w15.

JonaNN voor, or errmenn, GERMANY.

manana.

Specification' of Letters atent.

rnocns's non nnYING Bonnns AND THE Linn Patented Apr. 6, i915.

Application filed October 25, 1913. Serial No. 797,182.

To 'LZZ whom 'it may concern:

Be it known that l, JOHANN Voer, a citizen of the Gennan Empire, residing at Gip- 'pingen, Wurttemberg, Germany, have 1nvented certain new and usefulq improvements in Procees for Drying Boards and the like, of which the following a specilfication.

The splitting and cracking of freshly sawed boards, planks deal boards and wood in general during drying has ever been felt to be a defect, arising partly from the unequal density of the wood and partly from the gradual process of drying of the wood during its progress from the surface 'tol the center. lf a freshly cut board, taken from the center of a tree, is laid 11p-for drying, one may observe, that it contracts as the drying process goes on, not only as' to its width lbut also in its length, which latter is not generally known. This contraction lengthwise of the wooden fibers, however, does not occur uniformly but it is more considerable near the edges than in the center."

Moreover it is found, that the cells of trunks, left uncut fdr any length of time, will have dried much quicker near the bark than those in the center of the trunk, producing likewise an4 unequal contraction of the vol ume. rlhe result of such irregular reduction of the volume and contraction of the ib'ers must naturally be a certain tension inthe wood. which will find its release by the cracking of the boards as soon as the limits of elasticity are exceeded. As a result a board is liable to split into two crescent-shaped parts-the interior one being smaller by 5% than'the exterior one, which consists of heart-wood.V

The purpose of this present invention is to prevent the formation of these air-cracks (drying cracks) on the face as well as within the boards.

lf we are able to retard the drying of the layers near the bark which are more liable to contraction than those near lthe center,

than the latter will chielycontract in a lbn- .gitudinal direction ofthe fibers and attain the desired degree of dryness without any bending of the wooden fibers, because the central layers form one whole in such case, which contract mutually or toward each other, while the exterior soft layer of wood -is forced to contract toward the rigid center layer.

Figure l shows. the arrangement' of the they supports when the air current enters at the ends of the boards. Fig. 2 shows the ar! across the boards. The transverse ledges b have the eect, that the air does not brush ,past .the entire width of the boards, but chieiiy and without hindrance passes over themfalong the center. t0n the other hand it will be found that/the air is banked up in the cells, formed by the transverse ledges,

.with the result that less moisture is being absorbedirom the outside of the boards in a longitudinal direction than by the shorter current of air which passes over the center of the boards longwise.

According as the transverse ledges are placed, the outer parts of the boards will take double the time or even longer for a complete desiccation than the center parts.

there is still another peculiarity of the supporting ledges to be referred to which is eminently calculated to further the aims j in view, viz the property of these staple ledges a -and"b of directly hampering their drying influence, which arises from the mauner of placing them Yon the longitudinal faces ofthe boards, or vice versa', whereby.

not only the covered spots themselves but also the longitudinal fibers of the Wood on eitherside are checked in drying. lf, for instance, somebeech boardsare ,taken off .the transverse supporting ledges, upon which had-rested already'for some time, beforebeingfully dry, it will be observed that the boards are still more or less `damp 1n those places, and near them, on which they had rested, whereas the moredistant spaces` between the staple ledges are fully dry. This may readily -be explalned by the fact, that the air is prevented from exerting its drylng influence upon all such places of the boards which ,are covered by staple ledges. the "same wayldoes the humidity contained 1n the staple ledges themselves retard thev drying of the places nearest to them on the boards; besides this it should be noted that the dam in the staple ledges a and b is continua ly being renewed by the action of rain etc., with the effect, that the drying of the surrounding layers of wood is likewise retarded. This peculiarity of the stapleledges, which hampers the drying of the longitudinal sides of the boards, contributes to the fact, that the edges of the boards (nearthe bark c) as well as the partially covered lateral layers of the boards, which are protected by the transverse staple ledges, are still far from being dry while the center of the board has become dry and rigid, because protected from all outside moisture (rain etat) andcontinually. exposed to the -current o air passing along it.

. It is also possible to retard complete drying of parts near the bark more or less by givingvto the staple ledges aV and b a corresponding form reducing the places of contact. In like mannerone may protect the outside ofthe boards, deals etc. ina rational way from a too speedy drying by regulating the 'distances of the several transverse staple ledges in accordance with the percentage of water', hardness and structure of the wood to be dried. On'the yother hand one may contrive to accelerate or retard the drying of the center layer, according to necessity, by

vforming a wider or a narrower air channel with larger or smaller apertures in the longitudinal sides of the board (along the center layer.)- In the place, of wooden ledges one may employ strips 4of cardboard or duly shaped stencils.

As shown by Fig. 2 the longitudinal staple Vhat I claim and desire to secure by Letters Patent is:

1. The herein described process of drying boards, beams and the like which consists in drying the center pc rtions before drying the outer portions.

2. The herein described process of drying boards, beams and the like which consists in subjecting the board, beam or the like to the action of a current of air and retarding the drying of the outer portions.

3. The herein described process of drying boards, beams and the like which consists in causing an air current to traverse the board, beams or the like in the direction of its length and impeding the progress of the current adjacent the outer portions of the board beam or the like.

4. The herein described process of drying boards, beams and the like which consists in placing the boards, beams or the like in superposed relation and spaced from one another by spaced supporting members positioned adjacent their outer portions whereby longitudinally extending passages are formed between adjacent boards, and causing a heated medium to pass through said passages and into the spaces between said supporting members.

In testimony whereoI aiix my signature in presence of two witnesses.

- JOHANN VOGT. Witnesses:

JEAN GULDEN,

Riemann WOBBLINGER. 

